15... e7g6  16. f4e4 The rook occupies a central position. This is an active square, but it also leaves the rook open to an attack by the f-pawn. 16... b8a6 Gukesh decides to finish development. He could also try the advance of the f-pawn: 17. e1c2 Not the square I expected for the knight. 17... d8c7 A calm move.